Chevrolet CHEVY VAN G10 SERIES Service Manual page 160

a. C rank engine until m ark on torsional dam per lines
up w ith center or " O " m ark on the tim ing tab
fastened to th e crankcase fro n t cover an d the engine
is in th e num ber 1 firing position. This may be
determ ined b y placing fingers o n the num ber
valve as th e m ark on th e dam per com es near the
" O" m ark o n the crankcase fro n t cover. I f the
valves are n o t moving, th e engine is in th e num ber
firing position. If th e valves move as the m ark
com es up to the tim ing ta b , the engine is in num ber
6
firing position and should be tu rn ed over one
m ore tim e to reach the n um ber
b. With the engine in th e n um ber 1 firing position as
determ ined above, th e follow ing valves m ay be
adjusted.
E xhaust — 1 , 3 ,4 ,
Intake — 1, 2, 5, 7
c. Back o u t adjusting n u t u n til lash is felt at the push
rod th en tu rn in adjusting n u t until all lash is
rem oved. This can be determ ined b y checking push
ro d side play while turning adjusting n u t (Fig.
When play has been rem oved, tu rn adjusting n ut in
one full additional tu rn (to center lifter plunger).
d. C rank th e engine one revolution until th e pointer
" O " m ark and torsional dam per m ark are again in
alignm ent. This is n um ber
the engine in this p osition the following valves may
be adjusted.
E xhaust — 2, 5,
Intake -
4. Install rocker arm covers as outlined.
5. A djust carburetor idle speed.
V A L V E LIFTERS
H ydraulic valve lifters very seldom require atten tio n . The
lifters are extrem ely simple in design, readjustm ents are n o t
necessary, and servicing o f th e lifters requires only th a t care
and cleanliness be exercised in th e handling o f parts.
Locating Noisy Lifters
Locate a noisy valve lifter by using a piece o f garden hose
approxim ately four feet in length. Place one end o f the hose
near the end o f each intake an d exhaust valve w ith th e other
en d o f th e hose to th e ear. In this m anner, th e sound is
localized m aking it easy to determ ine w hich lifter is at fault.
A nother m eth o d is to place a finger on th e face o f the valve
spring retainer. I f th e lifter is n o t functioning properly, a
distinct shock will be felt w hen the valve return s to its seat.
The general types o f valve lifter noise are as follows:
1. H ard Rapping N oise— Usually caused by th e plunger
becom ing tight in the bore o f th e lifter body to such an
ex ten t th a t th e retu rn spring can no longer push the
plunger back up to w orking position. Probable causes
are:
a. E x c e ssiv e varnish
abnorm al stickiness.
b. Galling or " pick-up" betw een plunger an d bore o f
lifter b o d y , usually caused by an abrasive piece o f
dirt or m etal wedging betw een plunger an d lifter
body.
1
position.
8
6
firing position. W ith
6
, 7
6 ,8
3 , 4 ,
or carbon deposit causing
2. M oderate Rapping Noise— Probable causes are:
a. Excessively high leakdow n rate.
b. Leaky check valve seat.
c. Im proper adjustm ent,
1
3. General Noise T hroughout the Valve T rain—This will, in
m ost cases, be caused by either insufficient oil supply or
im proper adjustm ent.
1
4. In te rm itte n t C licking-P robable causes are:
a. A m icroscopic piece o f dirt m om entarily caught
betw een ball seat and check valve ball.
b. In rare cases, the ball itself m ay be out-of-round or
have a flat spot.
c. Im proper adjustm ent.
In m ost cases where noise exists in one or m ore lifters all
lifter units should be rem oved, disassembled, cleaned in a
solvent, reassem bled, and reinstalled in the engine. I f dirt,
corrosion, carbon, etc. is show n to exist in one u n it, it m ore
likely exists in all th e units, thus it w ould only be a m atter o f
tim e before all lifters caused trouble.
8
V).
Removal
1. Remove intake m anifold as outlined.
2. Remove valve m echanism as outlined.
3. Remove valve lifters.
N O T E : Place valve lifters in a rack so they may be
reinstalled in the same location.
Installation
1. Install valve lifters.
2. Install intake m anifold as outlined.
3. Install and adjust valve m echanism as outlined.
V A L V E STEM O IL SEAL and/or V A LV E SPRING
Replacement
1. Remove rocker arm cover as outlined.
2. Rem ove spark plug, rocker arm and push rod on the
cylinder(s) to be serviced.
3. In stall a ir lin e a d a p te r T o o l J -2 3 5 9 0 to s p a rk plug
p o r t a n d ap p ly co m p re sse d a ir to th e sp a rk p lu g h o le
to ho ld th e valves in place.
4. Using Tool J-5892 to com press th e valve spring, remove
th e valve locks, valve cap and valve spring an d dam per
(Fig. 9V).
5. Remove th e valve stem oil seal.
6
. Assemble as follows:
a. Set the valve spring and dam per, valve shield and
valve cap in place. The closely coiled end o f the
spring is installed
Com press th e spring w ith T ool J-5892 and install oil
seal in the low er groove o f the stem , making sure
the seal is flat and n o t tw isted.
N O T E : A light coat o f oil on the seal w ill help
prevent twisting.
b. Install the valve locks an d release the com pressor
to o l making sure th e locks seat properly in th e
upper groove o f th e valve stem .
ENG INE 6-31
against th e cylinder head.
C H E V Y V A N SH O P M A N U A L